In 1853, the Home Secretary, Lord Palmerston, published regulations for the new cemeteries established under the Metropolitan Burial Act 1852. Here's how they looked published in the Illustrated London News in December of that year:
I don't recall a whole bunch from my Anglo-Saxon history classes, but I do remember Simon Keynes talking about how laws prohibit what people were actually doing; there's no point, after all, in prohibiting something people aren't doing. He was talking about the instruction that vegetation be cut back as far as a bow's shot from roads, this demonstrating the existance and method of Anglo-Saxon highway robbery, but it's equally applicable to Palmerston's instructions.
Firstly, in Palmerston's "deletorious emanations", we see the miasmatic theory still current. Miasma theory held that diseases were caused by bad air, poor sanitation and foul water. Edwin Chadwick, the Victorian social reformer, said "all smell is disease", and miasma theory helped to explain why diseases like cholera were so prevalent in areas where drinking water or food and sewage intermingled. Of course, the theory is wrong - but it did spur many of the sanitary improvements in 19th century London which helped to reduce the incidence of diseases like cholera.
Trees, it was believed, helped to stop the spread of miasma. An article from the Illustrated London News of 1847 comments on Brompton Cemetery:
A rich vegetation exercises a powerful purifying influence, and where the emanations are moderate, as from single graves, would go far to prevent the escape of any deletorious miasma.
Hence the injunction to keep burials away from the boundaries of cemeteries and to plant trees on the margins; it's not for privacy or landscaping, it's for disease-prevention.
But the majority of Palmerston's concern is aimed at burials themselves, establishing the position and size of the plot, its security of tenure and its accurate recording. This is a direct reaction to practise in the City churchyards where bodies might be buried for a matter of months before being dug up to free space for a new incumbant, or where pits might be kept open for months, new burials being added on top of old.
The rules apply even when the freehold of the plot has not been purchased: i.e. they're valid for the poor just as much as for the rich. They're a remarkably progressive set of rules.